Method and apparatus for encoding and modulating data for wireless transmission

ABSTRACT

A wireless communications assembly and method for encoding and modulating data for transmission is provided. The method includes receiving primary data to be transmitted to a receiving station; selecting a data rate at which to transmit the primary data; selecting a mode associated with the data rate, the mode defining a modulation scheme and a target code rate; generating encoded data, including modifying an error correcting block format having a predefined code rate to generate the encoded data at the target code rate; and extracting at least a portion of the encoded data for modulation of a carrier signal and transmission to a receiving station.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from U.S. provisional application No.62/482293, filed Apr. 6, 2017, and U.S. provisional application No.62/500828, filed May 3, 2017, the contents of which are incorporatedherein by reference.

FIELD

The specification relates generally to wireless communications, andspecifically to a method and apparatus for encoding and modulating datafor wireless transmission.

BACKGROUND

Certain wireless communications protocols, such as those in theInstitute of Electrical and Electronics Engineers (IEEE) 802.11 familyof standards, define a variety of features, some of which may bemandatory and others of which may be optional. In particular, the 802.11standards define various modulation and coding schemes to encode dataand modulate a carrier signal to achieve different data rates fortransmission. Certain modulation schemes increase spectral efficiency,but may lead to increased transmission error rates.

SUMMARY

An aspect of the specification provides a method in a wirelesscommunications assembly of a transmitting station. The method includesreceiving primary data to be transmitted to a receiving station. Themethod further includes selecting a data rate at which to transmit theprimary data. The method further includes selecting a mode associatedwith the data rate, the mode defining a modulation scheme and a targetcode rate. The method further includes generating encoded data,including modifying an error correcting block format having a predefinedcode rate to generate the encoded data at the target code rate. Themethod further includes extracting at least a portion of the encodeddata for modulation of a carrier signal and transmission to thereceiving station.

BRIEF DESCRIPTIONS OF THE DRAWINGS

Embodiments are described with reference to the following figures, inwhich:

FIG. 1 depicts a wireless communications system;

FIG. 2 depicts certain internal components of a wireless device of thesystem of FIG. 1;

FIG. 3 depicts a method of encoding and modulating primary data fortransmission in the system of FIG. 1;

FIGS. 4A and 4B depict example constellation diagrams;

FIG. 5 depicts a method of generating encoded data in the system of FIG.1; and

FIG. 6 depicts a sequence of data bits in the system of FIG. 1.

DETAILED DESCRIPTION

FIG. 1 depicts a wireless communications system 100, including aplurality of wireless devices 104 (also referred to as stations 104). Inparticular, FIG. 1 illustrates a transmitting station 104-1 connectedwith a receiving station 104-2 via a bidirectional wireless link 112.The stations 104-1 and 104-2 are configured to both transmit and receivesignals, and are referred to as transmitting and receiving in thecontext of a single transmission. The transmitting and receivingstations 104-1 and 104-2 may be access points such as a wireless router,a media server, a home computer, a client device configured as a softaccess point and the like, or client devices, such as mobile devicessuch as smartphones, tablet computers and the like. More generally, thestations 104-1 and 104-2 can include any suitable combination ofcomputing devices with wireless communication assemblies suitable forcommunicating with one another. Thus the wireless connection 112 may beestablished between the wireless devices 104 illustrated in FIG. 1, aswell as any additional wireless devices (not shown) included in thesystem 100.

In the examples discussed below, the stations 104 of the system 100 eachinclude a wireless communications assembly configured to implement ashared wireless communication standard. In the present example, thestations 104 of the system 100 are each configured to communicateaccording to a wireless standard selected from the IEEE 802.11 family ofstandards. More specifically, the stations 104 are each configured tocommunicate according to the 802.11ay enhancement to the 802.11adstandard, both of which employ carrier frequencies of around 60 GHz(also referred to as mmWave). As will be apparent to those skilled inthe art, the discussion below may also be applied to a wide variety ofother communication standards.

Turning now to FIG. 2, before describing the operation of the stations104, certain components of a generic station 104 will be described. Aswill be apparent, the description of the station 104 below also appliesto each of the stations 104-1 and 104-2. That is, the stations 104-1 and104-2 each include the components discussed below, though it will beunderstood that the particular implementation of each component may varyfrom device to device.

The station 104 includes a central processing unit (CPU), also referredto as a processor 200. The processor 200 is interconnected with anon-transitory computer readable storage medium, such as a memory 204,having stored thereon various computer readable instructions forperforming various actions. The memory 204 includes a suitablecombination of volatile (e.g. Random Access Memory or RAM) andnon-volatile memory (e.g. read only memory or ROM, Electrically ErasableProgrammable Read Only Memory or EEPROM, flash memory). The processor200 and the memory 204 each comprise one or more integrated circuits.

The station 104 also includes one or more input devices and one or moreoutput devices, generally indicated as an input/output device 208. Theinput and output devices 208 serve to receive commands for controllingthe operation of the station 104 and for presenting information, e.g. toa user of the station 104. The input and output devices 208 thereforeinclude any suitable combination of devices, including a keyboard, amouse, a display, a touchscreen, a speaker, a microphone, cameras,sensors, and the like). In other embodiments, the input and outputdevices may be connected to the processor 200 via a network, or maysimply be omitted.

The station 104 further includes a wireless communications assembly 212interconnected with the processor 200. The assembly 212 enables thestation 104 to communicate with other computing devices. In the presentexample, as noted earlier, the assembly 212 enables such communicationaccording to the IEEE 802.11ay standard, and thus transmits and receivesdata at frequencies of around 60 GHz.

The communications assembly includes a controller 216 in the form of oneor more integrated circuits, configured to establish and maintaincommunication links with other devices (e.g., links 112). The controller216 is also configured to process outgoing data for transmission via oneor more antenna arrays, of which an example antenna array 220 isillustrated (e.g. a phased array of antenna elements). The controller216 is also configured to receive incoming transmissions from the array220 and process the transmission for communication to the processor 200.The controller 216, in the present example, therefore includes abaseband processor and a transceiver (also referred to as a radioprocessor), which may be implemented as distinct hardware elements orintegrated on a single circuit.

Further, the controller 216 is configured to execute variouscomputer-readable instructions (e.g. stored on a memory elementintegrated with the controller 216 or implemented as a discrete hardwarecomponent of the assembly 212 and connected with the controller 216) inthe form of a control application 224 for performing the functionsdescribed herein. The control application 224 may be implemented as asoftware driver executed within the assembly 212. Via the execution ofthe application 224, the controller 216 is configured to operate thewireless communications assembly to establish connections with thewireless communications assemblies of other devices 104. In particular,the controller 216 is configured to encode and modulate primary data ortransmission to the receiving station 104-2.

Turning now to FIG. 3, a method 300 of encoding and modulating primarydata for transmission is provided. The method 300 will be described inconnection with its performance on a station 104, and in particular at atransmitting station 104-1, as illustrated in FIG. 2. The blocks of themethod 300 are performed by the controller 216 of the communicationsinterface 212, via the execution of the application 224.

At block 305, the transmitting station 104-1, and in particular thecontroller 216, receives primary data to be transmitted to the receivingstation 104-2. For example, the primary data may be received from theprocessor 200 via execution of an application, such as a messagingapplication, a video streaming application or the like, of thetransmitting station 104-1.

At block 310, the controller 216 selects a data rate at which totransmit the primary data. For example, the controller 216 may select adata rate based on at least one of: the size of the primary data,capabilities of the transmitting station, capabilities of the receivingstation, and other characteristics of the primary data.

At block 315, the controller 216 selects a mode associated with the datarate, the mode defining a modulation scheme and a target code rate. Thetarget code rate defines a ratio of information bits to total number ofbits at which the primary data is to be encoded. Specifically, the totalnumber of bits may include a number of parity bits generated duringencoding for error correction during transmission. The mode alsoprovides a modulation scheme for modulation of the carrier signal basedon the encoded data. For example, the controller 216 may be configuredto select a given mode based on at least one of: selected data rate,encoding and modulation capabilities of the transmitting station 104-1,and decoding and demodulation capabilities of the receiving station104-2.

In some implementations, a shared wireless standard, such as the802.11ay standard, may define modulation and coding schemes (MCS) modesthat can be selected for encoding and modulating the primary data. Forexample, each mode may define a particular combination of MCS index,modulation scheme, target code rate, data rate, and other properties formodulation. Several example MCS modes are provided in Table 1.

TABLE 1 MCS Modes Normal Number of GI Data MCS 8-PSK MCS ModulationCoded Bits Rate Mode Applied Index Scheme per Symbol Repetition CodeRate (Mbps) 12 0 12 π/2-16- 4 1 1/2 3080 QAM 12a 1 12 π/2-8-PSK 3 1 2/33080 13 0 13 π/2-16- 4 1 5/8 3850 QAM 13a 1 13 π/2-8-PSK 3 1 5/6 3850

The MCS modes may be stored in a discrete hardware component of theassembly 212 and connected with the controller 216, or stored in amemory element integrated with the controller 216.

The modulation schemes may be represented by constellation diagrams. Theconstellation diagrams include constellation points which representpossible symbols that the modulation scheme may select to represent thedata for modulation. The constellation diagrams representing theπ/2-16-QAM and the π/2-8-PSK modulation schemes are shown respectivelyin FIGS. 4A and 4B.

Further, the geometry of the constellation points is representative ofcertain aspects of the modulation scheme. In particular, the powerrequired to transmit a certain symbol is represented by the distance ofthe corresponding constellation point to an origin of the constellationdiagram. The peak power of the modulation scheme is defined as the powerof the symbol having its corresponding constellation point at thegreatest distance from the origin. The average power is defined as theaverage power of all the symbols.

In some implementations, such as the π/2-8-PSK modulation scheme shownin FIG. 4B, the modulation scheme is represented by a circularconstellation diagram having constellation points equidistant from theorigin. In particular, circular constellation diagrams have a peak powerequal to the average power, hence the PAPR is minimized. In contrast,the π/2-16-QAM modulation scheme shown in FIG. 4A is represented by arelatively denser constellation diagram, which allows for higherspectral efficiency, however the PAPR is higher than that of theπ/2-8-PSK modulation scheme. To accommodate the higher PAPR, a lowercode rate may be used to allow for more parity data for errorcorrection.

In particular, for 60 GHz implementations, front end components may bepeak power limited. Hence, at lower peak-to-average power ratios (PAPR),power amplifiers can transmit more average power, low noise amplifiersand mixers may be less sensitive to interference, and lower dynamicranges and fewer bits of resolution can be implemented foranalog-to-digital converters and digital-to-analog converters. Moregenerally, at a higher average output power relative to a non-circularconstellation, modulation using circular constellations may be moretolerant of amplifier distortion. Hence, when the mode defines amodulation scheme having a circular constellation diagram, the antennaarray 220 may subsequently be controlled to transmit the modulatedcarrier signal at a power level substantially matching the peak power ofthe circular constellation diagram.

Returning to FIG. 3, at block 320, the controller 216 generates encodeddata. Specifically, the controller 216 modifies an error correctingblock format having a predefined code rate to generate the encoded dataat the target code rate. For example, the encoder may be configured toshorten the block format, as described herein, puncture the block formatby removing parity bits to increase the predefined code rate to thetarget code rate, or otherwise modify the block format to generate theencoded data at the target code rate.

Turning now to FIG. 5, a method 500 of generating encoded data byshortening the error correcting block format is provided.

Generally, the error correcting block format includes an informationportion having a predefined information portion length and a parityportion having a predefined parity portion length. Together, theinformation portion length and the parity portion length form the blocklength. In particular, the information portion length and the parityportion length are defined such that the ratio of the informationportion length to the block length is the predefined code rate of theblock format. The controller 216 is configured to populate theinformation portion with at least a portion of the primary data inaccordance with the predefined information portion length of the blockformat. The controller 216 is further configured to generate parity datafor populating the parity portion. Thus, the controller 216 encodes theprimary data according to the predefined code rate of the block format.

More particularly, at block 505, the controller 216 populates ashortened information portion of the information portion with at least aportion of the primary data. A portion of the primary data may beextracted for populating the shortened information portion in accordancewith length requirements of the shortened information portion, as willbe described further herein. Specifically, the shortened informationportion represents the portion of the primary data to be encoded fortransmission, and is shorter in length than the information portionlength defined by the block format as described above.

At block 510, the controller 216 populates a filler portion of theinformation portion with filler data. For example, the controller 216may populate the filler portion with zeroes or ones as filler data. Thefiller portion pads the shortened information portion to form theinformation portion. Specifically, the filler portion length and theshortened information portion length sum to the information portionlength as defined by the block format.

At block 515, the controller 216 populates the parity portion of theblock format. Per general operating procedures, the controller 216encodes the information portion by generating parity bits or parity datato allow for forward error correction during transmission. Specifically,for the given block format, the controller 216 requires the informationportion to have an information portion length as defined by the blockformat. Since the shortened information portion padded with the fillerportion have lengths summing to the information portion length definedby the block format, the controller 216 generates parity data forpopulating the parity portion using software and/or hardwarepreconfigured to process the block format. Specifically, the softwareand/or hardware used in current systems may be used without furthermodification to accommodate the length of the shortened block format.Hence, the controller 216 generates encoded data based on theinformation portion containing the primary data in the shortenedinformation portion, and the filler data in the filler portion. Thecontroller 216 may employ error correcting codes such as low-densityparity-check (LDPC) codes, Reed-Solomon codes, Golay codes or the like.

As described above, the information portion and the parity portion formthe error correcting block format. The predefined code rate of the blockformat is defined by the ratio of the information portion length to theblock length. Similarly, the shortened information portion and theparity portion form a shortened error correcting block format. The coderate of the shortened block format is defined by the ratio of theshortened information portion length to the shortened block length. Inparticular, the shortened information portion and the filler portion areselected such that the code rate of the shortened block format matchesthe target code rate.

At block 520, the encoder 224 provides the shortened information portionand the parity portion for modulation of the carrier signal andtransmission to the receiving station. In particular, the encoder 224discards the filler portion of the information portion and only providesthe shortened block format for further processing. Thus, the encoder 224provides the encoded data at the target code rate.

Generally, shortening the block format includes stuffing or padding thefiller portion of the information portion with filler data. The fillerportion allows the encoder 224 to generate the parity data and encodethe information portion according to existing coding schemes. The fillerportion is subsequently discarded so that the ratio of the shortenedinformation portion to the shortened block length matches the targetcode rate.

In some implementations, the predefined code rates may be defined instandards such as the 802.11ay standard, or the 802.11n standard. Inother implementations, code re-use and shortening may apply to coderates having longer block lengths. For example, where the block lengthis doubled, the number of information bits and the number of stuffedfiller data (i.e. zeros or ones) may also be doubled.

In some implementations, when a predefined code rate cannot be shortenedto exactly match the target code rate, the predefined code rate may beshortened to a code rate which is close to the target code rate. In suchimplementations, the encoder 224 may be configured to fill the fillerportion with filler data to pad the information portion to anappropriate information portion length.

FIG. 6 depicts a sequence 600 of data bits as they are modified duringthe method 500. Note that the data bits represented are exemplary; thelengths of the sequences and ratios between portions are not shown asthey generally would appear in a practical implementation.

Bits 605 include primary data bits D extracted from the primary data.Specifically, at block 505, the controller 216 populates primary databits D in the shortened information portion 601 which has length L1.

Bits 610 include the primary data bits D and filler bits F.Specifically, at block 510, the controller 216 generates the filler bitsF to populate the filler portion 602. The filler bits F pad the primarydata bits D in the shortened information portion 601 fill theinformation portion. The information portion has length L2.

Bits 615 include the primary data bits D, the filler bits F, and paritybits P. At block 515, the controller 216 generates parity bits P basedon the primary data bits D and the filler bits F to populate the paritybits P in the parity portion 603. Specifically, the controller 216encodes the primary data bits D and the filler bits F according toconventional methods requiring L2 number of bits for encoding. Theprimary data bits D, the filler bits F, and the parity bits P arepopulated in the block format having length L3.

Bits 620 include the primary data bits D and the parity bits P. At block520, the controller extracts the primary data bits D and the parity bitsP as the encoded data for modulation. Specifically, the primary databits D in the shortened information portion 601 and the parity bits P inthe parity portion 603 are extracted to form the shortened block formathaving length L4.

The predefined code rate of the block format is defined by the ratioL2/L3. The block format may be shortened into a shortened block formatin accordance with method 500. In particular, the information portion isshortened from L2 to L1 by discarding filler bits F in the fillerportion 602. Accordingly, the block format is also shortened from L3 toL4. Hence, the code rate of the shortened block format is defined by theratio L1/L4. L1 is specifically chosen so that the ratio L1/L4 matchesthe target code rate.

Frame 625 includes a header H and the bits 620. In some implementations,the header H includes a mode indicator indicating the mode selected atblock 315. The mode indicator allows the receiving station 104-2 todemodulate the carrier signal and decode the encoded data according tothe appropriate modulation and coding scheme. In particular, thereceiving station 104-2 receives shortened encoded data and populatesthe shortened information portion and the parity portion per thereceived signal. To accommodate the shortened encoded data, thereceiving station 104-2 populates the filler portion with the fillerdata, simulating perfectly received filler data. The receiving station104-2 thus has a fully populated block format which may be decodedaccording to existing decoding schemes.

For example, in the 802.11ay standard, the mode indicator may beincorporated into header bits in the legacy header, the EDMG Header A orthe EDMG Header B.

In other implementations, the transmitting station 104-1 and thereceiving station 104-2 may communicate capabilities and the selectedmode through the mode indicator and/or through capabilities fields, suchas an organizational unique identifier (OUI), through a specialinformation element defined by an entity such as the Wi-Fi Alliance,through a special information field defined by a manufacturer or thelike.

Returning to FIG. 3, at block 325, the controller 216 extracts a portionof the encoded data for modulation of a carrier signal and transmissionto the receiving station. In particular, the extracted portion of theencoded data has the target code rate.

At block 330, the controller 216 modulates the carrier signal using theextracted a portion of the encoded data according to the mode selectedat block 315.

For specific examples, reference is made to the MCS modes defined inTable 1.

In particular, the MCS mode 12 is defined to be modulated using theπ/2-16-QAM scheme at a code rate of 1/2, which results in a Normal GIdata rate of 3080 Mbps. In accordance with the present disclosure, analternate MCS mode 12 a is defined to be modulated using the π/2-8-PSKscheme at a code rate of 2/3, which results in an equivalent Normal GIrate of 3080 Mbps.

In particular, the MCS mode 12 a provides a smaller constellationdiagram, but is transmitted at a higher code rate. The code rate of 2/3is generated by shortening the existing 3/4 LDPC code as defined in the802.11ad standard. Specifically, the 3/4 code rate having block length672 bits (i.e. 504 information bits and 168 parity bits) is shortened bypadding the filler portion with 168 zero bits to fill the informationportion. After the filler portion is discarded, 336 information bits and168 parity bits remain, resulting in the target code rate of 2/3. Thecircular nature of the 8-PSK constellation diagram results in a lowerPAPR, allowing the carrier signal to be transmitted at a higher averagepower, and resulting in a net gain. In particular, as compared to the16-QAM modulation scheme, the 8-PSK modulation scheme requires about 0.4dB more in signal-to-noise ratio (SNR), but can be operated at about3.25 dB higher average power.

In another example, the MCS mode 13 is defined to be modulated using theπ/2-16-QAM scheme at a code rate of 5/8, which results in a Normal GIdata rate of 3850 Mbps. In accordance with the present disclosure, analternate MCS mode 13 a is defined to be modulated according to theπ/2-8-PSK scheme at a code rate of 5/6, which results in an equivalentNormal GI data rate of 3850 Mbps.

In particular, the MCS mode 13 a provides a smaller constellationdiagram, but is transmitted at a higher code rate. The code rate of 5/6is generated by shortening the existing 7/8 LDPC code as defined in the802.11ad standard. For example, the 7/8 code rate having block length672 bits (i.e. 588 information bits and 84 parity bits) is shortened bypadding the filler portion with 168 zero bits to fill the informationportion. After the filler portion is discarded, 420 information bits and84 parity bits remain, resulting in the target code rate of 5/6. Thecircular nature of the 8-PSK constellation diagram results in a lowerPAPR, allowing the carrier signal to be transmitted at a higher averagepower, and resulting in a net gain. In particular, as compared to the16-QAM modulation scheme, the 8-PSK modulation scheme requires about 0.6dB more in SNR, but can be operated at about 4.15 dB higher averagepower.

Thus, the MCS modes 12 a and 13 a may permit the same transmissionbandwidth while requiring lower peak power, which may reduce bit errorrate, particularly in 60 GHz devices, and other devices which have peakpower limits in the transmitting station 104-1 and/or the receivingstation 104-2.

Other MCS modes, such as those from Legacy DMG or IEEE 802.11ad, mayalso be extended to define further alternate modes. Otherconstellations, such as 16APSK as an alternative to 16QAM, 32APSK as analternative to 16QAM or 64QAM are also contemplated.

In some implementations, the mode may define a modulation scheme andcode rate which do not employ an integer number of information bits pertransmitted symbol (constellation point). For example, the mode may bedefined to use the 8-PSK modulation scheme with a code rate of 5/8. Inparticular, the combination of 8PSK with a code rate of 5/8 would resultin a data rate providing a mode in between MCS modes 11 and 12.

Thus, the present disclosure provides a system and method for encodingand modulating data for transmission. In particular, alternate modesprovide smaller constellations transmitted at a higher code rate, ascompared to existing modes. The alternate modes result in an equivalentdata rate, and can be transmitted at a higher average power, resultingin an overall increase in range and/or efficiency. The alternate modescan also result in a reduction in implementation cost and complexity.Further, a method of shortening existing code rates is provided to allowexisting encoders, such as LDPC encoders, to employ existing algorithmsto generate encoded data at new target code rates.

The scope of the claims should not be limited by the embodiments setforth in the above examples, but should be given the broadestinterpretation consistent with the description as a whole.

1. A method in a wireless communications assembly of a transmittingstation, the method comprising: receiving primary data to be transmittedto a receiving station; selecting a data rate at which to transmit theprimary data; selecting a mode associated with the data rate, the modedefining a modulation scheme and a target code rate; generating encodeddata, including modifying an error correcting block format having apredefined code rate to generate the encoded data at the target coderate; and extracting at least a portion of the encoded data formodulation of a carrier signal and transmission to the receivingstation.
 2. The method of claim 1, wherein the error correcting blockformat has an information portion and a parity portion, and whereingenerating encoded data comprises: populating a shortened informationportion of the information portion with at least a portion of theprimary data; populating a filler portion of the information portionwith filler data; and populating the parity portion of the errorcorrecting block format with parity data, the shortened informationportion and the parity portion defining a shortened error correctingblock format; wherein a ratio of an information portion length to ablock length matches the predefined code rate, and wherein a ratio of ashortened information portion length to a shortened block length matchesthe target code rate.
 3. The method of claim 2, wherein extracting atleast a portion of the encoded data comprises extracting the shortenedinformation portion and the parity portion of the encoded data formodulation of the carrier signal and transmission to the receivingstation.
 4. The method of claim 1, further comprising providing a modeindicator in a header of a frame containing the encoded data, the modeindicator indicating the selected mode.
 5. The method of claim 1,further comprising modulating the carrier signal using the portion ofthe encoded data, according to the modulation scheme.
 6. The method ofclaim 1, wherein the modulation scheme is represented by a circularconstellation diagram having constellation points equidistant from anorigin of the constellation diagram.
 7. The method of claim 6, furthercomprising: modulating the carrier signal using the portion of theencoded data according to the modulation scheme; and transmitting themodulated carrier signal at a power level substantially matching a peakpower of the modulation scheme.
 8. A wireless communications assembly ofa transmitting station, the wireless communications assembly comprising:an antenna array; and a controller interconnected with the antennaarray, the controller configured to: receive primary data to betransmitted to a receiving station; select a data rate at which totransmit the primary data; select a mode associated with the data rate,the mode defining a modulation scheme and a target code rate; generateencoded data, including modifying an error correcting block formathaving a predefined code rate to generate the encoded data at the targetcode rate; and extract at least a portion of the encoded data formodulation of a carrier signal and transmission to the receivingstation.
 9. The wireless communications assembly of claim 8, wherein theerror correcting block format has an information portion and a parityportion, and wherein the controller is configured to generate encodeddata by: populating a shortened information portion of the informationportion with at least a portion of the primary data; populating a fillerportion of the information portion with filler data; and populating theparity portion of the error correcting block format with parity data,the shortened information portion and the parity portion defining ashortened error correcting block format; and wherein a ratio of aninformation portion length to a block length matches the predefined coderate, and wherein a ratio of a shortened information portion length to ashortened block length matches the target code rate.
 10. The wirelesscommunications assembly of claim 9, wherein the controller is configuredto extract the shortened information portion and the parity portion ofthe encoded data for modulation of the carrier signal and transmissionto the receiving station.
 11. The wireless communications assembly ofclaim 8, wherein the controller is configured to provide a modeindicator in a header of a frame containing the encoded data, the modeindicator indicating the selected mode.
 12. The wireless communicationsassembly of claim 8, wherein the controller is further configured tomodulate of the carrier signal according to the modulation scheme. 13.The wireless communications assembly of claim 8, wherein the modulationscheme is represented by a circular constellation diagram havingconstellation points equidistant from an origin of the constellationdiagram.
 14. The wireless communications assembly of claim 13, whereinthe controller is further configured to: modulate the carrier signalaccording to the modulation scheme; and control the antenna array totransmit the modulated carrier signal at a power level substantiallymatching a peak power of the modulation scheme.